The present invention relates to a method to estimate a transmission channel characteristic, a transmission channel characteristic estimating arrangement able to perform this method, and a related remote terminal.
Such a method to estimate a transmission channel characteristic and related equipment are already known in the art, e.g. from the U.S. Pat. No. 4,105,995, entitled ‘Digitally Controlled Transmission Impairment Measurement Apparatus’. Typically, the operator needs knowledge of certain channel characteristics of a transmission channel between a central office and a remote terminal to be able to guarantee a certain service to a subscriber that has installed the remote terminal. The presence of line imperfections such as bridged taps, line attenuation, ageing effects, disturbers like radio frequency interference, and so on, has to be estimated by the operator before a certain quality of service can be guaranteed. To estimate all basic parameters necessary to characterise a transmission channel for its ability to carry data traffic, U.S. Pat. No. 4,105,995 describes a portable microprocessor controlled apparatus that measures specified parameters for a telephone channel. The known apparatus for channel characteristic estimation either consists of two units to be connected respectively to both ends of the transmission channel, or of a single unit to be connected to a single end of the transmission channel. The latter embodiment of the known channel characteristic estimating apparatus requires manual loop-back at the end of the transmission channel whereto the apparatus is not coupled. Summarising, U.S. Pat. No. 4,105,995 describes dedicated transmission channel test equipment enabling off-line measurement of channel characteristics. To apply the known technique, transmission of user data over the transmission channel has to be interrupted and test equipment has to be connected to the transmission channel either at one or at both sides of the channel.